alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Tendrit CnC Beacon 1"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/css.ashx?"; depth:10; http.uri.raw; pcre:"/^[a-z]{2,}=(?:%[A-F0-9]{2})+&/R"; http.header_names; content:!"Referer|0d 0a|"; reference:md5,755dad1f37a9d3fae1352dbbc409102c; reference:url,pwc.blogs.com/cyber_security_updates/2014/12/festive-spearphishing-merry-christmas-from-an-apt-actor.html; classtype:command-and-control; sid:2019985; rev:3; metadata:attack_target Client_Endpoint, created_at 2014_12_22, deployment Perimeter, signature_severity Major, tag c2, updated_at 2020_05_14, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)